The present invention concerns a method and device for locally linking optical and acoustic signals in an audiovisual apparatus.
Speech and sound reproduction in audiovisual apparatuses such as TV sets and monitors is currently performed through conventional dynamic speakers located outside the image area, mostly beside or below the screen apparatus. In speakers thus arranged, there is very little or no local linkage between the optical information displayed on the screen and the sound signals emitted by the speakers. Multichannel sound reproduction techniques, such as the xe2x80x9cDolby Surround Process,xe2x80x9d capable of bombarding the viewer from a plurality of directions on the horizontal plane, have been developed in the past, however, even this technique lacks direct local correspondence between the audio signals and the respective video signals. In other words, a viewer cannot receive the image and the corresponding sound signal from the same point on the screen.
Instead of placing the speaker outside the plane of the screen, German Offenlegungsschrift 3,832.616 discloses an electro-acoustic transducer with a piezopolymeric transparent film applied to the TV screen itself. Thus a correspondence between the spatial location of the screen and the transducer is achieved; however, the aforementioned arrangement is incapable of producing local linkage between a plurality of optical events on the screen and the corresponding sound signals as is desirable, for example, in videoconferences with a plurality of conference participants.
Therefore, the object of the invention is to provide a process and an arrangement comprising a plurality of electro-acoustic transducers to make improved linkage between optical and acoustic signals possible in an audiovisual apparatus with an image and sound reproduction device. Another object of the invention is to improve an electrostatic audio transducer so that it can be used in a transducer arrangement. A further object of the invention is to provide a device for local linkage between optical and acoustic signals encompassing a display and at least one electrostatic transducer integrated therein.
The present invention therefore provides a method for locally linking optical (video) and acoustic (audio) signals in an audiovisual apparatus with an image and sound reproduction device, wherein a plurality of electro-acoustic transducers are arranged in the immediate proximity of the image reproduction device. The transducers are electrically controlled independently of one another so that the optical events taking place in different image areas of the image reproduction device can be associated with the sound signals corresponding to the same locations, emitted by the respective electro-acoustic transducers.
The present invention also provides an arrangement comprising a plurality of electro-acoustic transducers, which can be used for locally linking optical and acoustic signals in an audiovisual apparatus with an image reproduction device. The electro-acoustic transducers are arranged in the immediate proximity of the image reproduction device and can be electrically controlled independently of one another so that the optical events taking place in different image areas of the image reproduction device can be associated with the sound signals originating at the corresponding locations and emitted by the respective transducers.
An electrostatic sound transducer for use in the arrangement is also provided. The sound transducer comprises an electrically conductive, transparent membrane, in particular, a plastic film, and a counter-electrode arranged at a predefined distance from the membrane.
The present invention also provides a device for local linkage between optical and acoustic signals with a display for representing the optical signals and at least one electrostatic transducer which has: an electrically conductive, transparent counter-electrode applied to the outer display layer; an insulating, transparent intermediate layer with a predefined elasticity so that it can experience small variations in thickness, applied to the conductive. transparent counter-electrode; and an electrically conductive, transparent membrane applied to the intermediate layer.
Further advantageous embodiments provide that a plurality of transparent transducers, which can be electrically controlled independently of one another, are arranged on the face of the image reproduction device in the form of a matrix. The transparent electro-acoustic transducers may be electrostatic and/or piezoelectric transducers, and may be integrated into the surface of the image reproduction device.
The electro-acoustic transducers also may be arranged alongside the image reproduction device and may be dynamic transducers. The transparent sound emitting elements, each one acoustically connected to one of the electro-acoustic transducers, may be arranged on the face of the image reproduction device.
The electro-acoustic transducers can be arranged behind the image reproduction device in the case of frontal projection of optical events onto the image reproduction device.
The transducers may also have an electrically conductive, transparent membrane, in particular, a plastic film, and a counter-electrode may be arranged at a predefined distance from the membrane. The counter-electrode may be a transparent metal grid, an electrically conductive glass or a metallized transparent plastic film. The electrically conductive glass may have a surface structured so that with the transparent membrane applied to said surface a plurality of small sound emitting elements are formed.
The surface of the image reproduction device may be electrically conductive and form the counter-electrode of the electrostatic transducer.
The present invention thus provides local linkage between video and sound signals in an audiovisual apparatus by having a plurality of electro-acoustic transducers arranged in the immediate proximity of the image reproduction device and electrically controlled independently of one another so that the optical events taking place in the different areas of the image reproduction device can be associated with the corresponding sound signals, emitted by the electro-acoustic transducers and originating from the respective locations. Thus a perceived coincidence of the video and sound signals for all image points can be achieved, since the electro-acoustic transducers emit the sound signals from the screen location where the corresponding visual information is produced.
Optimal linkage between optical and acoustic signals is obtained when a plurality of transparent transducers, electrically controlled independently of one another, are arranged in the form of a matrix on the face of the image reproduction device. Piezo-electric and/or electrostatic transducers can be used, for example, as transparent transducers.
Direct local image-sound linkage can be advantageously implemented by integrating the electrostatic transducers on the surface of the image reproduction device itself. In this case, the surface of the image reproduction device is made electrically conductive and serves as a counter-electrode for the transducer, which also has a transparent, electrically conductive membrane for emitting sound energy.
One important field of application for the present invention is videoconferencing. Efforts have been made for some time to develop ever larger screens capable of displaying the conference participants at actual size. The invention offers a considerable advantage here in that observing conference participants can always perceive the speech signal coming from the location on their screen where the conference participant speaking at the time is represented. Thanks to the transducer arrangement of the invention, speech comprehension in a videoconference can be improved and the quality of communication in general can be enhanced.